您好：
參考
https://ithelp.ithome.com.tw/articles/10209687
會出現ERR

https://i.imgur.com/3RtFPjt.png

請問，傳入字串是指

這邊嗎? 我改成

一樣會出現ERR

   <div id="app">
        <counter start="10"></counter>
    </div>


    <script src="https://cdn.jsdelivr.net/npm/vue@2.5.17/dist/vue.js"></script>
    <script>
        Vue.component('counter', {
            props: {
                start: Number,
            },
            template: `
                    <div>
                    <h1>{{count}}</h1>
                    <button @click="count+=1">按我</button>
                    </div>
                `,
            data() {
                return {
                    count: this.start,
                }
            }

        });

        new Vue({
            el: "#app"
        });
    </script>